It is known to use dual-mass flywheels having a pair of rotating masses which rotate freely relative to one another to a limited extent and are interconnected by a compliant member such as a spring damper system to lower the level of torsional vibrations generated by a firing internal combustion engine. The mass of the flywheel is split into a first mass and a second mass where the first mass is attached to the engine side of the damper system and the second mass is attached to a clutch/transmission side of the damper system. Dual-mass flywheels of this kind can improve overall vehicle driveability and increase the service life of various drive-train components. Drive-train vibrations are reduced by such dual-mass flywheels, which reduces rattling and droning noises, particularly at low engine speeds. The resultant smoother low-speed running allows comfortable driving at lower speeds, which helps reduce fuel consumption. The transmission is also easier to shift because of the low mass to be synchronized, and there is less synchronization wear.
A major problem with prior art dual-mass flywheels is that the natural frequencies of such systems are relatively low. This creates a problem when an engine is to be started in that the frequency of the torsional vibration excitation generated by the engine at some point in the engine start-up sequence, often below 400 rpm, matches the natural frequency of the dual-mass system causing high vibration levels and inhibiting the engine from reaching idle. When passing through a resonance frequency in the starting sequence of the engine there is the possibility that the two flywheels move in opposite directions and only stop finally when reaching end positions e.g. as the springs of a torsional vibration damper become “solid”, potentially causing degradation of the flywheel assembly.
The present disclosure describes a flywheel arrangement for an internal combustion engine producing a reduced level of torsional vibration during engine start-up, where the arrangement comprises a starter motor having a pinion gear at an output shaft, which pinion gear is arranged in constant engagement with a corresponding crank gear of a crank wheel located between an engine block and a flywheel assembly of the engine, which crank wheel is operatively connected to a crankshaft of the engine via a one-way clutch unit.
In one embodiment, the flywheel assembly comprises a first flywheel body adapted to be connected to the crankshaft of the engine, a second flywheel body which is rotatable relative to the first flywheel body and coupled thereto such that is able to move elastically through a limited angular distance relative to the first flywheel body, and an interlocking device including at least one locking arrangement adapted to produce an interlocking connection between the second flywheel body and the first flywheel body during cranking of the internal combustion engine.